In humans and other vertebrate animals the spinal column provides a protective channel to the upper body. The spinal column is made of individual vertebrae that are aligned together and extend along the center of the back. The vertebrae are movably joined at facet joints and are arranged in regions corresponding to the neck, thorax, and lower back. The arrangement within these regions provides the familiar spinal cord and supports the weight and posture of the individual while also enabling a wide range of motion along the curves and arches of the spinal column. To enable bending, twisting, and rotating of the upper body, the individual vertebrae are separated by intervertebral discs. The intervertebral disc are composed of tough fibrous connective tissue that ring around and surround a thick jelly-like material that makes up the disc. The disc acts to dampen shock transmitted along the spinal column and to enable motion. Spine curvature is arranged to accommodate all forces and weight placed on the spinal column. This is altered when vertebral bodies are fused, particularly at several levels, creating a flat back deformity.
Postoperative flat back deformity is caused by surgical intervention with fusion without correction for lordosis. The loss of lumbar lordosis with resulting sagittal imbalance has been recognized and termed flat back syndrome.
Intervertebral discs may become damaged or degenerate over time due to disease or abrupt injury such that it may become medically necessary to surgically remove the damaged or degenerated disc. To maintain the intervertebral spacing between two adjacent vertebrae from which the disc has been removed it has been shown to insert an intervertebral implant, onlay, or inlay grafts over the effected spaces to stabilized the same. The intervertebral implant has traditionally been used to promote bone ingrowth across the disc space and to fuse the adjacent vertebrae into a single structure. Allogeneic derived compact cancellous bone is the preferred implant material to promote bone ingrowth into the implanted graft from the adjacent vertebrae or processes. Compact cancellous bone is not pliable and good quality allogeneic derived compact cancellous bone is in short supply while having size limitations. Current supply of allogeneic compact cancellous bone is insufficient to accommodate a large number of patients in need of spinal fusions.